${\mathrm{C}}_5{\mathrm{H}}_{10}$ represents three isomeric alkenes ${\mathrm{A}}_1,{\mathrm{A}}_2$ and ${\mathrm{A}}_3$. Each on hydrogenation gives $2$-methylbutane. ${\mathrm{A}}_1$ and ${\mathrm{A}}_2$ on oxymercuration-demercuration give the same $3°$ alcool. ${\mathrm{A}}_2$ and ${\mathrm{A}}_3$ on hydroboration oxidation give different $1°$ alcohol. Assign structures to ${\mathrm{A}}_1,{\mathrm{A}}_2$ and ${\mathrm{A}}_3$ and explain reactions.